The typical finish on an automobile or truck body comprises an electrodeposited primer layer, an optional primer or primer surfacer layer over the electrodeposited layer and then a pigmented base coat layer and over the pigmented base coat layer, a clear coat layer is applied. A pigmented mono-coat may be used in place of the base coat/clear coat. A number of clear and pigmented coating compositions have been utilized as automotive OEM and automotive refinish coatings, such as, primers, basecoats and clear coats but none meet the rapid curing times that are desired in combination with outstanding physical properties, such as, high hardness and high crosslink density. Such coating compositions can, if desired, have low volatile organic content (VOC).
In refinishing automobiles and trucks, the damaged painted areas having dents, mars and scratches and the like are sanded or ground out by mechanical means in and around the damaged area. Sometimes the original coating is stripped off from a portion or off the entire auto or truck body to expose the substrate (e.g., bare metal) underneath. After repairing the damage, the repaired surface is coated and applied layers are dried and cured.
A key concern of the automobile and truck refinish industry is productivity, i.e., the ability to complete an entire refinish operation in the least amount of time. To accomplish a high level of productivity, any coatings applied need to have the combination of “snap dry” and “through dry” at ambient temperature conditions in a relatively short period of time. The term “snap dry” means that the resulting finish is physically dry to the touch in a relatively short period of time to minimize dirt pick-up and minimize contamination from other sources when the automobile or truck is removed from the spray booth or spray area. The term “through dry” means that the finish is sufficiently cured to allow buffing of the finish.
In automotive OEM, rapid dry and curing of a coating that forms a finish with excellent properties, such as, high coating hardness and crosslink density is very desirable since it is possible to reduce baking temperatures and baking times thereby decreasing productions costs.
Current commercially available coating compositions do not have these unique characteristics of rapidly curing under ambient temperature conditions along with the ability to form a finish having high coating hardness and crosslink density. It would be advantageous to have a coating composition with this unique combination of properties.